J/A+A/691/L20 Seismic diff. between solar magnetic cycles 23/24 (Garcia+, 2024)
Seismic differences between solar magnetic cycles 23 and 24 for low-degree
modes.
Garcia R.A., Breton S.N., Salabert D., Tripathy S.C., Jain K., Mathur S.,
Panetier E.
<Astron. Astrophys. 691, L20 (2024)>
=2024A&A...691L..20G 2024A&A...691L..20G (SIMBAD/NED BibCode)
ADC_Keywords: Sun ; Asteroseismology ; Magnetic fields
Keywords: Methods: data analysis - Sun: activity - Sun: helioseismology
Abstract:
Solar magnetic activity follows regular cycles of about 11 years with
an inversion of polarity in the poles every ∼22 years. This changing
surface magnetism impacts the properties of the acoustic modes. The
acoustic mode frequency shifts are a good proxy of the magnetic cycle.
In this paper, we investigate solar magnetic activity cycles 23 and 24
through the evolution of the frequency shifts of low-degree modes
(l= 0, 1, 2) in three frequency bands. These bands probe properties
between 74 and 1575 km beneath the surface. The analysis is carried
out by using observations from the space instrument Global
Oscillations at Low Frequency and the ground-based Birmingham Solar
Oscillations Network and Global Oscillation Network Group. The
frequency shifts of radial modes suggest that changes in magnetic
field amplitude and configuration are likely to occur near the Sun's
surface rather than its core. The maximum shifts of solar cycle 24
occur earlier at mid and high latitudes compared to the equator, about
1550km beneath the photosphere. At this depth but near the equator,
this maximum aligns with the surface activity but is stronger in
magnitude. At around 74km deep, the behaviour near the equator mirrors
the surface, while at higher latitudes, it matches the strength of
cycle 23.
Description:
We used three different datasets of velocity measurements. The
first one was collected by the Global Oscillations at Low Frequency
(GOLF) instrument on board the Solar and Heliospheric Observatory
(SoHO). We obtained 24.5 years of continuous data - from April 11,
1996, until September 4, 2020 - of Doppler velocity time series
following Garcia et al. (2005A&A...442..385G 2005A&A...442..385G) and ensuring a proper
timing of the measurements (for more details, see Appourchaux et al.
2018A&A...617A.108A 2018A&A...617A.108A; Breton et al. 2022A&A...658A..27B 2022A&A...658A..27B). The second
dataset was collected with the Birmingham Solar Oscillation Network
(BiSON2) starting at the same time as GOLF but extending only to April
4, 2020 and corrected following the procedure described in Davies et
al. (2014MNRAS.441.3009D 2014MNRAS.441.3009D). The third dataset is composed of Doppler
velocity measurements from the GONG network. The series in this third
dataset start on May 7, 1995, and are available through October 9,
2020, with a median duty cycle value of 87% (varying between 78 and
92%).
In Tables B.1, B.2, and B.3, the computed averaged frequency
shifts (δv) for modes l = 0, 1, and 2 are shown respectively for
GOLF, BiSON, and GONG.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 371 94 GOLF computed averaged frequency shifts
(δv) for modes l = 0, 1, and 2
tableb2.dat 371 94 BiSON computed averaged frequency shifts
(δv) for modes l = 0, 1, and 2
tableb3.dat 371 629 GONG computed averaged frequency shifts
(δv) for modes l = 0, 1, and 2
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See also:
J/A+A/617/A108 : Sun velocities from GOLF instrument (Appourchaux+, 2018)
Byte-by-byte Description of file: tableb1.dat tableb2.dat tableb3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 F17.12 yr Time Time
19- 37 F19.16 uHz dvLFB-l0 Averaged frequency shift for l=0 at
LFB (1800-2450uHz) band (freqshiftLFB_l0)
39- 56 F18.16 uHz e_dvLFB-l0 Error on dvLFB-l0 (errLFBl0)
58- 76 F19.16 uHz dvMFB-l0 Averaged frequency shift for l=0 at
MFB (2450-3110uHz) band (freqshiftMFB_l0)
78- 95 F18.16 uHz e_dvMFB-l0 Error on dvMFB-l0 (errMFBl0)
97-115 F19.16 uHz dvHFB-l0 Averaged frequency shift for l=0 at
HFB (3110-3890uHz) band (freqshiftHFB_l0)
117-134 F18.16 uHz e_dvHFB-l0 Error on dvHFB-l0 (errHFBl0)
136-157 E22.16 uHz dvLFB-l1 Averaged frequency shift for l=1 at
LFB (1800-2450uHz) band (freqshiftLFB_l1)
159-176 F18.16 uHz e_dvLFB-l1 Error on dvLFB-l1 (errLFBl1)
178-196 F19.16 uHz dvMFB-l1 Averaged frequency shift for l=1 at
HFB (3110-3890uHz) band (freqshiftMFB_l1)
198-215 F18.16 uHz e_dvMFB-l1 Error on dvMFB-l1 (errMFBl1)
217-235 F19.16 uHz dvHFB-l1 Averaged frequency shift for l=1 at
MFB (2450-3110uHz) band (freqshiftHFB_l1)
237-254 F18.16 uHz e_dvHFB-l1 Error on dvHFB-l1 (errHFBl1)
256-274 F19.16 uHz dvLFB-l2 Averaged frequency shift for l=2 at
LFB (1800-2450uHz) band (freqshiftLFB_l2)
276-293 F18.16 uHz e_dvLFB-l2 Error on dvLFB-l2 (errLFBl2)
295-313 F19.16 uHz dvMFB-l2 Averaged frequency shift for l=2 at
MFB (2450-3110uHz) band (freqshiftMFB_l2)
315-332 F18.16 uHz e_dvMFB-l2 Error on dvMFB-l2 (errMFBl2)
334-352 F19.16 uHz dvHFB-l2 Averaged frequency shift for l=2 at
HFB (3110-3890uHz) band (freqshiftHFB_l2)
354-371 F18.16 uHz e_dvHFB-l2 Error on dvHFB-l2 (errHFBl2)
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Acknowledgements:
Rafael Garcia, rgarcia(at)cea.fr
(End) Patricia Vannier [CDS] 31-Oct-2024